Write a review button not working

[remygreen]

I recently added the shopify review app to my store, whilst the review drop down menu is working the option at the bottom of the page is not - When you click 'write a review' the review form does not appear. I think it's to do with the code but I have no idea how to fix it. Please see the problem in the link below, any help much appreciated! 

https://remygreen.co.uk/products/am-botanic-serum